Portable power hammer



Oct. 21, 1941. A. G. DECKER, JR

PORTABLE POWER HAMMER 4 Sheets-Sheet 1 4 Sheets-Sheet 2 A. G. DECKER, JR

PORTABLE POWER HAMMER Filed, July 21, 1939 Oct. 21, 1941.

Oct. 21, 1941.

A. G. DECKER, JR PORTABLE POWER HAMMER Filed July 21, 1939 4Sheets-Sneet 3 1941- A. G. DECKER, JR 2,260,172

' PORTABLE POWER HAMMER- Filed Jui 21, 1959 4 Sheets-Sheet 4 PatentedOct. 21, 1941 UNITED STATES PORTABLE POWER HAMMER Alonzo G. Decker, Jr.,Towson,. Md., assignor to The Black and Decker Manufacturing Company, acorporation of Maryland Application July 21, 1939, Serial No. 285,681

16 Claims.

The present invention relates to a hand directed, supported andcontrolled power hammer of the general type shown in Baker Patent No.2,013,296. This is operated by an electric motor enclosed within thetool casing, but various features of the invention are capable ofapplication to portable hammers operated from other sources of power.While the ram in this type of hammer is operated by a crank andconnecting rod, it is dependent for the storage of energy at each strokeupon a spring which is either a coiledspring or a pneumatic spring or acombination of coil and pneumatic spring, to increase at the properinstance, the impact incident to the normal reciprocation by means ofcrank and con-- necting rod.

The improvement of the present invention relates particularly to themeans for storing and delivering this excess impact avoiding certaindefects which have come to be recognized as of importance.

In accordance with previous development in this art, the spring wasconcentrically loaded and for this purpose was provided with closedcoils at each end and there was sufficient clear ance between the outersurface of the piston body and the active coils which intervene betweenthe closed coils at the ends to eliminate wear. Outstanding defects ofthis design were found to be that the spring would break due to wearadjacent-the ends of the closed coils and due to concentration of stressat these points and a further defect was due to the fact that theunsupported end or ends of this spring wereof sufficient weight to causesurging or vibration due to the inertia of these parts of the springmade eifective by the rapid reciprocation. Surging results in excessstresses which also cause spring failure, also there was a tendency tobreak at the point between the closed coils where the springs wererigidly supported and the free portions where they were not sosupported.

The present invention provides a new spring arrangement and a new springin which the 45 closed coils at the end or ends have been elimi-' fnated resulting in a spring which must be loaded eccentrically and whichto avoid lateral bending is supported throughout its entire length,,thissupport is also of great benefit in that itprovides a dampening.action which not. only eliminates the effect of the weight and theinertia of. the spring during reciprocation but by its dampening actionit reduces or eliminates surging above referred to and it also has theeffect of reducing 5 the tendency to concentrate the stress adjacent theends where the closed coils occurred.

The invention also provides means for connecting the ram to the crosshead comprising a hollow ram which serves as a cylinder which receivesthe shank of a steel piston which'is made hollow and of an'enlargeddiameter to provide a frictional support for the spring throughout itslength. This construction is economical to manufacture and increases thelife of the piston on account of the feasibility of constructing it ofsteel and permits a large diameter piston shank for a given diameter ofspring which in turn 1ncreases the available size of the compressionchamber which connects the ram tothe cross head thus improving thehammer action. gOther telescoping members may be substituted for thecylinder and piston.

In accordance with an alternative construction which has considerableadvantages, a steel sleeve is pressed on to an aluminum or similar lightmetal piston, which sleeve serves as a support for the springandthesteel ram is trepanned providing for the compression of the springwithoutcausing the supporting sleeve to strike the ram. I

In these constructions it-has been found that due partly to the increasein the size of the piston shank and consequently the size of the compression chamber, the ram tends to continue its motion and to strikeblows on the nose of the hammer when the drill bit has beenremoved. Toovercome this tendency means has been'provided to catch the ram andhold'it long enough to throw it out of synchronism with the cross headthereby reducing or preventing the 'recoilof the ram and thus stoppingthe hammer action. Two forms of ram checking means are shown.

In the accompanying drawings; I have illustrated so much-of a portablepower'driven-hammer aszis necessary toa full comprehension of theinvention in its various forms and of the manner of constructing,applying; operating and using the same.

In the drawings:

Fig. 1 is a longitudinal section on a plane of Fig. 1, the internalconstruction being shown in broken lines.

Fig. 6 is a section showing a modified construction, the View being'asection on a plane of the barrel axis, corresponding to Fig. 1.

Fig. 7 is a section on the line in Fig. 6.

Fig. 8 is an external elevation of a hammer of this type shown on areduced scale.

Fig. 9-

a fragmentary section on a plane of the barrel axis showing a modifiedform of friction ring for checking the motion of the ram to throw it outof synchronization.

Fig. 10 is a section on the line le -w in Fig. 9.

Fig. 11 is a view corresponding. ta Fig. 1 taken on the barrel axis,showing a, slightly modified form of nose and spring expansion ring. forchecking the ram and throwing it out of synchronization.

Fig. 12 is a section on the line |2- |2 ea are partsioftheouter casingwhich also includes field casing l, andbrush housing or casing 5-. The:gear casing and the: field casing are shown as detachable and the brushhousing-inthe form shown'is'integral with the field casing. Theillustration-also includes a handle or grip 6 attached tothe crarikcaseand to' thefield casing;

the handleor grip inthe form; shown being provided with a switchoperating trigger I and a cord protector 8 enclosing the inner end{ of ithe cable 9i a In the form illustrated iii-Fig; 5. an electric motor Iisenclosed within the field casing. The motor i I0 isprovid'ed with acoolingfan- H and-connected by -geaiis |2,' to and with a crank l-fl'a-nd crank I pin I152 which operates a connecting-rod l6 whichreciprocates a cross head'- H, to which" it is connected bywrist pin N3,the crosshead havinga suitable guide 1 9 which in the form shown 'i'nFig. 1 is integral with the ram guide andsomewhat' larger in crosssection.- The term erossghead is, however, i not strictly limited 'to a"crank operatedmember similar reciprocation being other-wise obtainable.The arrangement above defined is: known practice capable-of widevariation and not essential tattle-invention;

=Referring-particularlyto Figs; 1 "and; 2; the barrel I is jprovided'With a nose 24 at its lower end which in theform shownis-threaded intothelower end' 'of the barrel and provided with a bit socket or guide 22which is aligned with the axis of the bar'rel The 'ramfgu'ide Zil'WhiCh:is a meter tube iii an cord. with the existing practice istlrireadjed orotherwise secured at its ends at 2-4 and-fZ-S Within the barrfiel "whichprovides a jacket 23 or cool-.

ing space aboutfthefguide 'and said jacket'is ventilated 'at 2-1 Therain- 1s connected; to the cross head H by 'meansof a cylinder andpistons." In t'he "construction shown in- Fig; 1,

fit in the genius and provide for ventingthespace beneath the ram, 'and'the crcsshead' is similarly vented at to avoid impounding air within thebarrel.

The operation of the parts thus described is more fully explained in theabove cited patent.

The cross head I! has formed integral therewith a piston 36 whichcontrols a suitable compression space 32 within the cylinder 3| and aspring 38 is compressed between the cylinder 3| and the. cross head ll,whereby energy is stored in the spring and by compression beneath thepiston 36 to be released in synchronism with the normal reciprocation ofthe cross head as in the above cited'patent. The action of the cylinderand piston. providing alternate compression and vacuum at 32. combinedwith the action of spring 3;; provides aresilient means between thecross head and ram whereby motion is transmitted tothe cross head fromthe ram and the ram is vibrated relatively to the cross head as thelatter reciprocates. The spring 38 as shown is secured at its upper endin groove 33- formed inan enlarged portion 41 at the-upper end or thepiston. The spring 38 which is of l ielic-al form t'ermi nates in ahelically arranged end porti'orififl which bears against the lowersurface of the cross head- H- and has! its operative portion Mfrictionally engaged with the: enlarged bar-rel 36"" of piston 36 whichis hollow at 3:1 to provide ire-- duc ed weight with sufficientdiametertdengage the spring-whereby the spring is permitted} tocontract andexpand but" is: frictionally engaged for purposes of dampening. Thelower end 'of this spring 38 at 43. is 'helically'arranged and atitsextreme end 43" bears against the-top: sur

which is grooved at 39 to engage the spring and the lower end of thespring at 43", and the fricti'onallyengaged portion 42 moves along" thepiston as. the spring contracts and expands and the cylinder and pistonmove one relatively to the other.

The frictional. supporting f-uncti'on prevents lateral bending of thespring, i. e;, the bending of the spring toone side asthe load isapplied and also prevents surging of the spring giving What may betermed adampening'acti'on eliminating: the. effect ofweight of thespring particularly the closed coil formerly employed This method alsoavoids: the concentration. of

stress due to-having the ends of't-hese springs in v closed coils forloading purposes. -It willalso be noted that the shank of the piston 36is'hollowed out toreduce its weightpermitting it to bemade of sufiicientsize-to support the spring frie tionally. This method of constructionprovides for economical manufacture and increases: the

lifefof the piston and permits it: to be maderofs hard; metal as steelinstead ofthe; lighter metals: and. that it increasesthesize of thecompres-.-

sion chamber which improvesthe action ofthe;

ram.

It has been. found, due to. the. increasedsize of the piston orpi'stonshank and the. conse- I quent increased size of the compression chamben.

the ram has a tendency to continue. to strike blows on the nose 2i of'the hammer. after the drill bit has been removed. To overcome thistendency means has been providedinthe pathof.

theram beyond its normal. stroke butwithin the the strokewhich is'performed in the absence of a bit, said means beingadapted to check orprevent the recoil of the'ram as it passes beyond its normalstroke. Bym'erely'checking the recoil of the ram, it is thrownout'of'synchronization with'the vibrations of the spring and the motionof the cross head, the hammering action of the rain, in idling, beingthus either prevented or so reduced that it becomes harmless.

For this'purpose, inthe form of the invention now being discussed anexpanding sleeve 48 has been provided as shown in Figs. 1, 3 and 4, andthis sleeve 48'which is also referred to as a ring, is divided into sixsegments 49 by six slots 49' which as shown are parallel to the axis andextend downwardly from the top edge 49" to a portion 50 at the lower endwhich is thickened and threaded internally and externally at 50 and. 50"respectively, the internal threads 50' in theform shown engage the noseand the external thread engages the inside of the ram guide near the endwhereby the ring is turned down against suitable packing at provided ona peripheral upturned shoulder 52 on the nose 2|, the nose in turnhaving a threaded engagement at 53 with the inner surface of the lowerend of the barrel I.

The-sleeve or ring 48 is shown as int'ernallytapered at its upper end at54 being thus adapted to engage the lower end of the ram 30 which iscorrespondingly tapered at 55, the internal diameter of the sleeve orring 48 being slightly less than the external diameter of the ram, thuswhen the bit or star drill is removed the ram moves forward ordownwardly it is forced into the expanding sleeve or ring 48 and held bythe sleeve long enough to throw the ram out of synchronism with thepiston and cross head I! thus checking the tendency of the ram to buildup hammer action due to the combined synchronized action of the springand vacuum in the chamber 31 with the cross head'motionwhichsynchronized action is explained in the prior patent above cited.

Figs. 6 and 7 illustrate a modified form of the construction in whichthe ram Ell-is formed with an upwardly extending piston 6| which fits ina cylinder 62 formed in a cylinder casting 65 carried by and attached tothe cross head 63, being in this instance formed integrally with thecross .head which fits and slides in the ram guide 59.

In this case a steel sleeve 64 is pressed onto and outside of the outersurface of the cylinder casting- 65 which for lightness is of aluminumand thehead of the rank trepanned or grooved circumferentially about thebase of the piston at 66; providing for the entrance of the end of thesleeve 64. into this groove so that the spring 61 can'be' compressedbetween the ram and the cross head without causing the sleeve to strikethe head of the, ram, said head being indicated by reference character68. Thegroove 66 which extends cir-' cumferentiallyaround the baseof'the piston 6| is-parallel to the axis extending downwardly in adirection away from the cross head 63.

The sleeve 64 serves as a guide and as a dampener for the spring 6!which corresponds to the spring 38 in Fig. 1. The outer surface ofsleeve 64' serving the purpose of the outer surface of the piston 36 inFig. 2, i. e., as a guide for an eccentrically loaded spring and as adampener to prevent surging. I

It'will'be noted'that the cylinder 621s provided with vents 69 and tolimit the pressure and vacuum and-itheram head 68 1s grooved at 1| tocent the point of impact;

prevent accumulation of back pressure beneath the ram.

This is a highly satisfactory construction as to the details described,though the construction first described is preferred as capable ofproduction on a large scale at a relatively small cost. 1 Figs. 9 and 10illustrate a modified form of friction or expansion ring correspondingtothe ring 48 in Figs. 1, 3 and 4. These figures show a ram head 15 of thehollow type in a ram guide 13', which is grooved internally at 16, thegroove l6 being substantially parallel to a plane at right angles to theaxis of the tool, this groove contains a spring wire hexagonal ring 11which is of an internal diameter a little less than the externaldiameter of the ram head 15, so that theram head mayexpand the ring, asto' the centers of its hexagonal sides 19 as it advances towardthe'nose'8| when the bit is displaced. The spring ring is to prevent hammering ofthe ram on the nosezwhen the bit is removed and consequent injury to thetool.

It will be noted that the ram head 15 is shown ascircumferentiallygrooved as to its outer surface at which provides a seat and grip forthe ring 76 as the groove 80 passes said ring,'u sually engagin on theup stroke. a

As previously'noted in connection with the member 48 in Figs. 1, 3 and 4thepurpose of this construction is to check the recoilof the ram due tothe spring and/or vacuum-andpressure in the cylinder, etc., and toeither holdit in depressed position or to throw itout of synchronizationwith the 'reciprocationsof' thef'cross' head thus reducing in 'theabsence of a bit in operative engagement-with thework, the energyimparted to the ram on its descent. At other times the ram is stoppedby'th'e bit near the position shown in Fig. 1 so that the frictionexpanding sleeve or ring 48* or 16 is non-essential under suchcircumstances; i.' e. when the bit is in place and pressed against thework, and has no effect. When the bit is removed, however, the ramadvances to or" approaches the position shown in Fig. 9, groove BIJpassing ring 16 and on its return stroke the frictionor expansion ring16 becomes-effective to throw the vibrations of the. ram due to thespring 61' or 38 and/or the cylinder and piston: action'out of'synchronization with the recipro'cations' due to the action 'of thecrank andcross head reducing the stroke of the ram andthe power of thesame so that it does not"'advance into'contactwith-thenose 8|.

Figs. 6, 9 and 10"show vents 82near: the lower end of the ib'a'rrel,providing afpassage for theventilating air to"co6l'the guide and ramadja- Referrin'gnow-to Figs. 11, 12 and 13; Fig. 11 resembles'Figi' -1'except as to the type of friction expansion sleeve orr'ing 48in Fig. 1,for checking the recoil of the ram.

Figs. 11, 12 and 13 show the ram guide 20 grooved circumferentially at"83 near its lower end, the groove being parallel to a plane atrightangles to-the tool axis.v The barrel is indicated by reference characterI and the ram guide by reference character 20} 1 I The groove 83receivesthev spring expansion ring 84 which 'inthis instance is in theform of three relatively flat arcs 85' meeting at their ends atcontinuou's corner porticn s 85 these corners 85' are'deeply seated inthe groove 83, the middle portion of-th'e arcs-85 projecting from' thegroove into the guidespaceto be engaged'by the head 86' of the ra'm as"it approaches tlie-nose 81 on ,rnaliy on retunm strokm. eff-eel: beinthatthe delivery; on the energy; stonedi by: compression in the springand/or inz the; is

out/of. synchronization with: the normal reqinnocaztion ofi the crossheadi reducing". the: strekefandl anoidingf hammering: aetinm off theram head: on; the. nose: 81;: which would; otherwisetaliern aeerwhenthebitiis withdrawm The term cross head as used? hereina inchidesneeiproeating; member: op ratin hezramr hnql ehi and: her, way of: a2resilient. element and he erm nrma inelndesianmesilient meainssserw in asimila-r purpose.

t The improved operatiom amdrthe-advantagessre suiting-iron); the;v newconstructifine a bnae dislosed; av be n fully described amt dismissedthe, preambleandiingconneetiemwith: the: details of he rawmss;

The: preferred; and, severak. medifledE formsz of theginnentiqn and themanner oi 'oon'stnucting;

, applying operating amt'usingrthe: same injcone nation. with: a p w r:driyem hammer whereby thesesadvatages. aoerue' having been thus: described; specifically and; 1m detail; in; order that r h manneratcenstrutti ei app yin nenatin V ande 115m inyention' manbe. fill-1132slinden.

stood; thezspeeifie. terms; are: used: desexiptivel-y r her than in atlimi ing sense the: eonstruation shown bein e p b r oi wide'variationwithin the, spiritofi the: invention. v

I :elairm and; desire to secure: bwl'eettens Batentiis Q f a; n a. h ndcon r lled? and: supn r edx pow r. opera-ted of; the: type? described:having a r ciproca r s head: and a: ram and oo-' one t na eyi ndnranapiston membere conn ct-- mg the cross head: and: the: pistonibeing? hollow, anda spning coiled; aboutandzhavingasuppontithezspringragainstlateraliyielding i fir-iotionahengagementiwithr one: qiisaidt members 7 for; a snbstantia'lz portionofiits lengthgsaid spring being; in pressure transmitting; relation.atT-one' end with; the: cross head: and at the other enct with the ramsaid frictional enga ement,- serving to dampen the action of. theaspfiigiandpiievent. sur in an iram hecking: means be1ow' he:nor

'endl against the erase head -and atethe othen end.

against the; ram? and; tending, to 'advanee'the namgsaid spring beins,eccen ri yfloadedr a trictional;eneaeementservinete damneni the; ace7.5.

3; In a, handd'controlledi and supportedypowen operated hammer 0t thetype-2. described; haying a reciprocating cross; head". and; a ram withtelescoping: members between. the; cross: head. and ram, a substantiallyhelical. spring; encircling: one of said! members: and having:frictional engage-=- menti therewith;v and: adapted: to, apply; pressureat one end against the cross head; amt at'the otlien end against: therain: "and; tendin'gf to; advance: the;- ram, saidi frictional:engagement ex; tending: substantially throughout: ther'lengthoi?theespring betweem itsxbe-aringi on the oross1- head and the: bearing:om the: ram; and; serving; ta

dampen: the action "of-.7 the spring and: prevent slinging; the; springbeing: eccentripally; loaded? and. said: frictional contact also:serving toypreei ventlaterazhyieldingrofi theespring'. "r

4'. A power operaterhhammenoff theereciprodate i'ng type having a.reciprocating; cross: headfiand a. ram; teleseopingfmembers; and:resilient means: connecting the crosso heath itoz'tl'ietram to vibrate;the; ram: relatively to the: cross-z head: and: by synchronization to.aecentuatel thea blows diie: to thee reciprocation .ofi the: crossheazdi eheckin'g meanssinz the path of thezram operating beyond the endof the normal stroke of theram: to? checlc the: reooit off the whenzthertooli'is iiil ing'in the: absence ofiaibit'whereby; har'mfuli vhammering: in. idling is prevented: by stopping the ram: or: throwing:it out of synchronization with the; spningand crosse-headi I 5:. 'A-Lpowen' operated: hammer of? the re'ciproiel eating type having: a:reciprocating; crosshead: and amam: and" telesceping members and; aspiing cooperating; therewith: to transmit pressur'ez'fromi the:crosshea'ot to the ram to: vibrate the; rami relatively to: the I crosshead: and by-"synchrbniaaa tion to. accentuate the blows due to the:reeipr o cation. of? the cross head, friction: rneans in the path of theram: located beyond the end of the normal stroke of the ram tocheck therehound of the ram when thetool" is idling, said friction means beingrigidly: engaged with a statio'nary portionofthe-hammer. Y

eating type having a reciprocating prose head the blows due to thereciprocation of thecross hea d, friction means in the path of]therainif l operating beyond-"the end of the normalstroke of the ram tothrow" the vibrations of they due-to the'spri'ng action ont'ofsynehronizat n; with: the reeiprooation'sof the cross head when' the ramis idling; said frietion means being iii the.v form of ending in thepath off'the ram and? rig-idly: engaged with a stationary portion'of thehammer; the upper portion ofsaid ring beingtapered and the ring being ofslightly-less inff i ternal: diameter than the external 'diameterio'fthe ram and havingslots extending downwardly from: its: upper edge toprovide for yieldingto permit theentrance offtheram int'o-the ring. Apower operated hammer of- 'the reeipr-ol eating type having apositivelyopera-ted oi oss i head! and. a ram and telescopingi'memb'ers'and a: spring; cooperating: therewith: to corinect'th cross head to theram to vibrate-the; Tami-relate i'velfy, torthe crosst head anctby"synchroni'zati6n ti)- acoentuate the: blows due toithe recipnooatiom"Q i the r m fri-Q nngmeans the: path 6i power operatedliaznrner" of there -mm: V

ram located beyond the end of the normal stroke of the ram to throw thevibrations of the ram due to the spring action out of synchronizationwith the reciprocations of the cross head when the ram is idling, saidfriction means being in the form of a spring ring of less internaldiameter than the outside diameter of the ram near its lower end saidring encircling the path of the ram beyond its normal path and beingseated in a stationary portion of the tool.

8. A power operated hammer .of the reciprocating type having a crosshead and a ram, a ram guide and cylinder and piston members connectingthe cross head to the ram the piston being hollow, a spring coiled aboutone of said members to vibrate the ram relatively to the cross head insynchronization with the motion of the cross head and accentuate theblows due to the reciprocation of the cross head the spring being infrictional engagement with said member substantially throughout itslength said member being of the largest diameter which the guide willadmit and a ram checking device operating on the ram when it movesbeyond its normal stroke, said checking device serving to check therecoil of the ram when the hammer is idling in the absence of a bit.

9. A power operated hammer having a cross head, .a ram and telescopingmembers and a spring connecting the ram to the cross head and tending toadvance the ram, the spring being coiled about one of said members infrictional sliding engagement therewith substantially throughout itslength and secured thereto at one end and having its other end open andinclined and bearing against the other said member at its extremityonly.

10. In a power hammer of the type described having a cross head, a ramand cylinder and piston members and a spring connecting the cross headand ram to set up vibration of the ram relatively to the cross head, oneof said members being provided with a jacket overlapping the other saidmember, the spring being coiled about said jacket and frictionallyengaged therewith intermediately of and for a substantial proportion ofthe length of the spring.

11. In a power hammer of the type described having a cross head, a ramand cylinder and piston members and a spring connecting the cross headand ram to set up vibration of the ram relatively to the cross head, oneof said members being of light metal provided with a hard metal jacketoverlapping the other said member, the spring being coiled about saidjacket and frictionally engaged therewith intermediately of and for asubstantial proportion of the length of the spring one of said membersbeing grooved in line with the jacket to admit the end of the jacketwhen the spring is approaching full compression.

12. In a power hammer of the type described having a cross head and aram and cylinder and piston members and a spring connecting the crosshead and ram to set up vibration of the ram relatively to the crosshead, one of said members being of light metal with a hard metal jacket,the spring being coiled about said jacket and frictionally engagedtherewith intermediately of and for a substantial proportion of thelength of the spring.

13. In a hand controlled and supported, power operated hammer having tworeciprocating members comprising a cross head and a ram and a coiledspring in pressure transmitting relation at one end with the cross headand at the other end with the ram and tending to advance the ram, andmeans having telescoping engagement with one of said members and havingfrictional engagement with the coils of the spring substantiallythroughout the length of the spring, said frictional engagement servingto dampen the action of the spring and prevent surging.

14. In a hand controlled and supported power operated hammer having areciprocating cross head and a ram with telescoping guiding meanstherefor, a substantially helical spring transmitting pressure from thecross head to the ram and tending to advance the ram with the crosshead, said spring having a frictional engagement with one of saidtelescoping members throughout its length serving to dampen the actionof the spring and prevent surging, the spring being eccentrically loadedand said frictional contact also serving to guide and prevent lateralyielding of the spring.

15. In a hand controlled and supported power operated hammer, having apositively operated reciprocating cross head, a ram with resilient meansbetween the ram and the cross head and ram checking means in the path ofthe ram, said resilient means transmitting the motion from the crosshead to the ram and permitting vibration of the ram relatively to thecross head, said checking means being inoperative within the normalstroke of the ram, but engaging the ram when it moves beyond its normalworking stroke as in idling in the absence of a bit.

16. A power operated hammer of the reciprocating type having apositively operated cross head and a ram, and resilientmeans between thecross-head and the ram to reciprocate the ram and permit vibration ofthe ram relatively to the cross head as the latter reciprocates and toaccentuate the blows due to the reciprocation of the cross head, meansin the path of the ram located beyond the end of the normal stroke ofthe ram, said latter means being in the form of a spring ring of lessinternal diameter than the outside diameter of the ram near its lowerend, said ring encircling the path of the ramnear the lower end of itsstroke and means securing the ring in a stationary portion of the tool,said ring being adapted to be entered by the lower end of the ram and togrip the ram when it passes beyond its normal stroke.

ALONZO G. DECKER, JR.

